During imaging using magnetic resonance systems a peripheral stimulation of the nerves or heart may occur because of the gradient fields, if an imaging sequence with large magnetic field gradient changes is used. To prevent the stimulation, standardization bodies, for example ISO 60601-2-33, have called for limit values for the stimulation.
U.S. Pat. No. 6,169,403 B1 describes a method for predicting the stimulation value prior to a measurement and for monitoring it during a measurement. In this case, a magnetic flux vector differentiated by time is filtered multiple times per spatial direction, combined in a weighted manner, and evaluated against a limit. Mathematically, the filtering is effected by a convolution of the time characteristic of the time derivative with an e-function. Because of the computation rate, the convolution takes place by an iteration. During the iteration, the current filter value for the further processing is calculated at each time point from the preceding filter value. Because the calculation of whole measuring cycles during imaging has previously taken a very long time, the determination of the stimulation value has been restricted to the gradient sequence which would generate the highest stimulation. For safety reasons, a safety margin may additionally likewise be applied, which reduces the maximally permitted time derivative of the magnetic field gradients.